On Thu, Jul 14, 2016 at 05:20:55PM +0100, Emil Velikov wrote:
> On 14 July 2016 at 15:23, Eric Engestrom <eric.engest...@imgtec.com> wrote:
> > On Thu, Jul 14, 2016 at 03:21:20PM +0200, Stefan Dirsch wrote:
> >> This 'last' variable used in FindGLXFunction(...) may become negative,
> >> but has been defined as unsigned int resulting in an overflow,
> >> finally resulting in a segfault when accessing
> >> _glXDispatchTableStrings[...].
> >> Fixed this by definining it as signed int. 'first' variable also needs to
> >> be
> >> defined as signed int. Otherwise condition for while loop fails due to C
> >> implicitly converting signed to unsigned values before comparison.
> >
> > Indeed, `last` can become negative is when the name searched for is
> > alphabetically less than the first entry in the dispatch table.
> > On the penultimate round, we would have `first = 0` and `last = 1`.
> > Next iteration of the while loop, middle becomes 0, `strcmp() > 0`
> > and last = middle - 1, ie. -1.
> >
> > The same issue exists on the other side (name searched is after last
> > entry), but until DI_FUNCTION_COUNT reaches UINT_MAX this wouldn't
> > wrap around.
> >
> > It's unlikely we'll ever have more than INT_MAX entries in the dispatch
> > table, so I think this patch is OK. I tried to find a better fix, but
> > adding checks before updating first and last feels too heavy.
> >
> Indeed, reaching {U,}INT_MAX is extremely unlikely, thus we can avoid
> adding extra checks.
>
> > Reviewed-by: Eric Engestrom <eric.engest...@imgtec.com>
> >
> I'll add the stable tag and push this in a few minutes (as the fresh
> doze of coffee kicks in).
Thanks a lot!
> Stefan, I'll double-check about the issue mentioned in the cover
> letter and let you know (and/or send patches).
Didn't hear back from you. Are you still planning to look into this? Or does
it just work for you and I messed something up on my side?
Thanks,
Stefan
Public Key available
------------------------------------------------------
Stefan Dirsch (Res. & Dev.) SUSE LINUX GmbH
Tel: 0911-740 53 0 Maxfeldstraße 5
FAX: 0911-740 53 479 D-90409 Nürnberg
http://www.suse.de Germany
---------------------------------------------------------------
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham
Norton, HRB 21284 (AG Nürnberg)
---------------------------------------------------------------
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/mesa-dev
